Gates, one of the world's richest men and head of the Bill and Melinda Gates Foundation, met Prime Minister John Key at Bo'ao Forum in China during the weekend.

Yesterday Key said he and Gates had discussed the outlook for the US and New Zealand economies, Microsoft's work in education, and also the possibility that Gates' foundation might be interested in becoming involved in the search for a vaccine for rheumatic fever.

The inflammatory disease, which occurs after a streptococcal infection, is common in both New Zealand and Australia, which are now undertaking joint work on a vaccine. It also affects a number of Pacific countries, and Key said he sketched for Gates an outline of how an eradication plan might be part of an aid programme.

Gates is already involved in a bid to eradicate polio, another inflammatory disease which can damage the spinal cord and lead to paralysis.

Key admitted rheumatic fever was a different issue, but said Gates had said he would consider it.

"It's of a different scale and possibly a different scope to the eradication of polio, but the eradication of rheumatic fever is something that could be of interest to quite a number of parties, and [I] sort of sketched to him a sort of outline of how that could and might work," the prime minister said.

Earlier this year the Government pledged $3 million together with Australia for scientists to find a vaccine.

Whether a vaccine could be developed was uncertain Key said.

A pharmaceutical company had done extensive work before abandoning the project for commercial reasons, although Key said that with the New Zealand and Australian Governments now working on the plan, the same commercial pressures were gone.

Key is in China with one of New Zealand's largest business delegations to the country, to try and to build business relationships as New Zealand exports to the country have tripled in the five years since the signing of an historic free trade agreement.